It is highly recommended that your installation have a data set name table (ICHRDSNT). You can use ICHRDSNT to specify the number of resident data blocks for each data set in the primary RACF® database. (See The data set name table.)

If your installation does not have a data set name table, you can specify the number of resident data blocks for a single data set of the RACF database in ICHSECOP, or use the default value of 10 resident data blocks. However, be aware that using ICHRDSNT provides more flexibility and better performance options than using ICHSECOP.

If you have a data set name table and also have specified resident data blocks using ICHSECOP, the data set name table takes precedence during RACF processing.

You can select the number of RACF database data blocks to be made resident. An installation can specify from 0 to 255 resident data blocks; the default value is 10 resident data blocks. The blocks reside in ECSA.

Resident data blocks reduce the I/O processing that is required to service the RACF database. Each data block uses 4128 (4KB + 32) bytes of storage.